An electronic transmission control unit is a device that controls an automatic transmission. The transmission control unit generally uses sensors associated with the vehicle as well as data provided by an engine control unit to calculate how and when to change gears in the vehicle for optimum performance, fuel economy, and shift quality. With an electronic transmission control unit, an automatic transmission is able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed, and improved vehicle handling. The immense range of programmability offered by a transmission control unit allows the modern automatic transmission to he used with appropriate transmission characteristics for each application. Typically, an electronic transmission control unit includes an application specific integrated circuit (ASIC) or the like.
Traditionally, automobile transmission control units used custom-designed Application Specific Integrated Circuits (ASICs). One particular area where ASICs are used is to provide transmission control unit watchdog functionality, transmission relay power output control, undervoltage detection, and transmission delay counter and the associated logic. The watchdog functionality is included with the transmission control unit to ensure that the transmission control unit is functioning properly. For example, these ASICs can be configured to detect slow or fast timing over a watchdog window detect period. Additionally, these ASICs can control the output power of a transmission relay, provide reset and undervoltage detection, and the like. The transmission relay power output is used to energize solenoids in the transmission itself. Disadvantageously, these custom-designed ASICs have significant development costs, maintenance costs, and are complex to upgrade or add enhanced functionality to.